Treatment of thrombotic or atherosclerotic lesions in blood vessels using an endovascular approach has recently proven to be an effective and reliable alternative to surgical intervention in selected patients. For example, directional atherectomy and percutaneous translumenal coronary angioplasty (PTCA) with or without stent deployment are useful in treating patients with coronary occlusion. Atherectomy physically removes plaque by cutting, pulverizing, or shaving in atherosclerotic arteries using a catheter-deliverable endarterectomy device. Angioplasty enlarges the diameter of a stenotic vessel by exerting mechanical force on the vascular walls. In addition to using angioplasty, stenting, and/or atherectomy on the coronary vasculature, these endovascular techniques have also proven useful in treating other vascular lesions in, for example, carotid artery stenosis, peripheral arterial occlusive disease (especially the aorta, the iliac artery, and the femoral artery), renal artery stenosis caused by atherosclerosis or fibromuscular disease, superior vena cava syndrome, and occlusive iliac vein thrombosis resistant to thrombolysis.
It is well recognized-that one of the complications associated with endovascular techniques is the dislodgment of embolic materials generated during manipulation of the vessel, thereby causing occlusion of the narrower vessels downstream and ischemia or infarct of the organ that the vessel supplies. In 1995, Waksman et al. disclosed that distal embolization is common after directional atherectomy in coronary arteries and saphenous vein grafts. See Waksman et al., American Heart Journal 129(3): 430-5 (1995), (this and all other references cited herein are expressly incorporated by reference as if fully set forth in their entirety herein). This study found that distal embolization occurs in 28% (31 out of 111) of the patients undergoing atherectomy. In January 1999, Jordan, Jr. et al. disclosed that treatment of carotid stenosis using percutaneous angioplasty with stenting is associated with more than eight times the rate of microemboli seen using carotid endarterectomy. See Jordan, Jr. et al. Cardiovascular Surgery 7(1): 33-8 (1999), incorporated herein by reference. Microemboli, as detected by transcranial Doppler monitoring in this study, have been shown to be a potential cause of stroke. The embolic materials include calcium, intimal debris, atheromatous plaque, thrombi, and/or air.
There are a number of devices designed to provide blood filtering for entrapment of vascular emboli. The vast majority of these devices are designed for permanent placement in veins to prevent pulmonary embolism. A temporary venous filter device is disclosed in Bajaj, U.S. Pat. No. 5,053,008, incorporated herein by reference. The Bajaj device is an intracardiac catheter for temporary placement in the pulmonary trunk of a patient predisposed to pulmonary embolism due to, e.g., hip surgery, major trauma, major abdominal or pelvic surgery, or immobilization. The Bajaj device includes an umbrella made from meshwork that traps venous emboli before they reach the lungs. This device is designed for venous filtration and is not suitable for arterial use because of the hemodynamic differences between arteries and veins.
There are very few intravascular devices designed for arterial use. Arteries are much more flexible and elastic than veins and, in the arteries, blood flow is pulsatile with large pressure variations between systolic and diastolic flow. These pressure variations cause the artery walls to expand and contract. Blood flow rates in the arteries vary from about 0.1 to 5 L/min. Ginsburg, U.S. Pat. No. 4,873,978, discloses an arterial filtering system, which includes a catheter with a strainer device at its distal end. This device is inserted into the vessel downstream from the treatment site and, after treatment, the strainer is collapsed around the entrapped emboli and removed from the body. The Ginsburg device, however, is integral with the catheter, unlike the devices described later herein. Ing. Walter Hengst GmbH & Co, German Patent DE 34 17 738, discloses another arterial filter having a folding linkage system that converts the filter from the collapsed to the expanded state.
Filters mounted to the distal end of guidewires have been proposed for intravascular blood filtration. A majority of these devices include a filter that is attached to a guidewire and is mechanically actuated via struts or a pre-shaped basket that deploys in the vessel. These filters are typically mesh “parachutes” that are attached to the shaft of the wire at the distal end and to wire struts that extend outward in a radial direction at their proximal end. The radial struts open the proximal end of the filter to the wall of the vessel. Blood flowing through the vessel is forced through the mesh thereby capturing embolic material in the filter.
Gilson et al., International Publication No. WO 99/23976 describes a guidewire with a filter slideably mounted thereon. Although the filter is not fixed to the guidewire at a single point, the filter is limited in its range of movement by two stops at the distal end of the guidewire, the stops being relatively closely spaced. Thus, unlike the present invention, in Gilson et al. the filter cannot be removed unless the entire guidewire is removed.
The useful in vivo time of a guidewire filter will vary, depending upon the type of procedure, the patient, and the blood flow. These factors may contribute to relatively short use time because of, for example, blood coagulation or excessive emboli clogging the filter mesh. Because for existing devices, the guidewire and the filter are integrated into one inseparable device, changing the filter after its useful in vivo deployment time has been completed requires the removal and replacement of the guidewire. This change requires time consuming and costly fluoroscopic guidance to reposition the new guidewire and filter.
There is a need in the art for a device that will not require removal and replacement of the guidewire should the in vivo useful life of a blood filter be exceeded. The present invention addresses that need by providing a blood cartridge filter that may be used and replaced without requiring the removal of the guidewire.